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<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        var username = prompt("请输入用户名");
        var passweod = prompt("请输入密码");
        while (username != "admin" || passweod != "123456") {
            alert("登录失败");
            username = prompt("请输入用户名");
            passweod = prompt("请输入密码");
        }
        alert("登录成功");
    </script>
</body>

</html>